1. Field of the Invention
This invention relates to insulin-like growth factor I (IGFI) and insulin-like growth factor 2 (IGF2) chimeric polypeptides, methods of producing such polypeptides, and therapeutic methods for administering such polypeptides.
2. Description of Related Art
The insulin-like growth factors (IGFs) constitute a family of proteins having insulin-like and growth stimulating properties. Human IGFI (also known as somatomedin C) is a 70 aa basic peptide (pl 8.4) having the protein and DNA sequences shown in SEQ ID NOs:1-2, and has a 43% homology with proinsulin (Rinderknecht et al. (1978) J. Biol. Chem. 253:2769-2776). Human IGF2 is a 67 amino acid basic peptide having the protein and DNA sequences shown in SEQ ID NOs:3-4. Specific binding proteins of high molecular weight having very high binding capacity for IGF1 and IGF2 act as carrier proteins or as modulators of IGF1 functions (Holly et al. (1989) J. Endocrinol. 122:611-618).
IGFI and IGF2 and variants thereof have been used to treat humans suffering from growth hormone deficiencies, tissue wasting, burns, skeletal trauma, infection, cancer, cystic fibrosis, Duchenne, muscular dystrophy, Becker dystrophy, autosomal recessive dystrophy, polymyositis, as well as myopathies and AIDS (U.S. Pat. No. 5,622,932). IGF fusion proteins composed of portions of both IGF-1 and IGF-2 have been used as therapeutics for targeting the brain (US 2003/0072761).